To find the ratio of the NS-NS merger in CEJSN (very-early mergers) to all CCSNe, I start with the fraction of NS-NS merger out of all CCSNe, \(f_{\rm Me/CCSN}\) , and multiply it by \(f_{\rm EMe/Me}\) . From the results of [1]} that give the rate of NS-NS merger per unit stellar mass formation, the fraction of NS-NS mergers to CCSNe is \(f_{\rm Me/CCSN} \approx 3 \times 10^{-5} - 8 \times 10^{-4}\) .
The fraction of NS-NS merger in CEJSN to CCSN is therefore
\(\begin{aligned}& f_{\rm EMe/CCSN} \equiv \frac{\rm Very~early~mergers}{\rm CCSNe}\\ & \simeq f_{\rm EMe/Me} \times f_{\rm Me/CCSN} 10^{-6} - 2 \times 10^{-5}.\end{aligned}\) 
